1. Field of the Invention
This invention relates to an arrowhead with interchangeable blades that can operate as either a fixed-blade arrowhead or a blade-opening arrowhead having at least one blade which is pivotally mounted to move between a fully open position and a fully closed position wherein there is a positive snap locking blade retention system that maintains each blade in a normally closed position.
2. Description of Prior Art
In the archery industry, many manufacturers have attempted to simultaneously achieve an arrowhead that has aerodynamic properties similar to those associated with non-bladed arrowheads known as field points or nib points, while also achieving effective cutting areas provided by bladed arrowheads, which are often referred to as broadheads. Broadhead blades which are exposed during flight often result in undesirable steering of the front portion of the arrow, causing the arrow to deviate from a perfect flight path that coincides with a longitudinal axis of the arrow shaft, when loaded or drawn within an archery bow.
By reducing the surface area of a broadhead blade, the undesirable steering effects can be reduced. However, when the surface area of a blade is significantly reduced, the structural integrity is diminished. Also, by reducing the surface area of a blade, the cutting area within a target or game is also reduced, resulting in a less effective entrance and exit wound.
Conventional blade-opening arrowheads have been designed so that a substantial portion of the blade is hidden within the body of the arrowhead, such as during flight of the arrow. Upon impact, such blades are designed to open and thereby expose a cutting surface or sharp edge of the blade. When the blades of such conventional arrowheads are closed and substantially hidden within the body, the exposed surface area is reduced and thus produces relatively less undesirable steering effects.
Many of such conventional blade-opening arrowheads rely upon complex mechanisms, some of which fail to open because of a significant holding or closing force that must be overcome, and others that open prematurely because of structural deficiencies within the blade carrying body that fail upon impact, resulting in non-penetration of the arrow. With such relatively complex mechanisms, dirt or other materials that may enter such conventional arrowheads can affect the reliability of the arrowhead, particularly after prolonged use.
Other conventional broadheads which have blades partially hidden within the body use annular retaining rings, such as O-rings, wraps, bands and the like, in order to maintain the blades in a closed position during flight. Upon impact, such annular retaining rings are designed to sheer or roll back alone the opening blades, in order to allow the blades to move to an open position. Quite often, such conventional annular retaining rings are prone to cracking, particularly when the elastomer material dries out. Upon release of a bow string, the rapid acceleration and thus significant opening forces move the blades in an opening direction. The conventional annular retaining rings counteract such opening forces. However, when the ring material dries out, cracks or is otherwise damaged, the blades may open prematurely, resulting in significant danger or injury to the archer.
Many of the annular retaining rings are designed for one use and thus must be replaced after each use. In addition to the cost involved with supplying such consumable item, the annular retaining ring is difficult and time-consuming to install, such as when hunting, particularly during inclement weather. Furthermore, the material properties of such conventional annular retaining rings can be affected by temperature changes, thereby resulting in different bias forces that cause the blade to open prematurely or to not open when desired.
U.S. Pat. No. 5,090,709 teaches an arrowhead with extendable blades positioned adjacent fixed blades. The extendable blades are pivotally connected to a body. A ring releasably holds the extendable blades within corresponding slots within the body.
U.S. Pat. No. 5,286,035 teaches an arrowhead that has a sharpened blade, pivotally mounted within a slot in the body of the arrowhead. A rubber O-ring is used to hold the blade in a temporarily stationary position, centered within the slot in the body. Upon impact, the rubber O-ring slides rearward onto the arrow shaft and allows the blade to pivot to either side of the arrowhead body.
U.S. Pat. Nos. 5,112,063, 4,998,738 and 5,082,292 each disclose a broadhead with deployable cutting blades that are connected by pivot pins to a plunger. The cutting blades pivot between an open cutting position and a closed non-barbed position.
U.S. Pat. No. 5,102,147 discloses a ballistic broadhead assembly that has blades pivotally mounted on an actuating plunger. Upon impact, the actuating plunger thrusts the blades outwardly and forwardly.
It is apparent from the conventional blade-opening arrowheads that there is a need for a blade-opening arrowhead that maintains each blade in a closed and locked position during flight, and that allows the blades to responsively free-wheel to an open position when a sufficient opening force is applied to the blade. It is apparent that there is a need for a blade-opening arrowhead that does not require consumable items, such as 0-rings, wraps, bands and the like, to hold the blades in a closed position. It is also apparent that there is a need for an arrowhead that will accommodate fixed blades in addition to and/or in lieu of pivotally mounted blades for example to accommodate dull practice blades or other sharpened fixed blades.
It is one object of this invention to provide an arrowhead with interchangeable blades wherein a dull blade or a sharpened blade can be interchanged with a pivotally mounted blade.
It is another object of this invention to provide an arrowhead with pivotally mounted blades that can be maintained in a normally closed position, wherein a major portion of each blade is housed within a slot of the blade carrying body, and that pivot rearwardly into a fully open position upon target impact or upon experiencing a similar opening force.
It is another object of this invention to provide an arrowhead with pivotally mounted blades that each have a rounded, blunt tip portion that is the portion of the blade that initially contacts a target.
It is another object of this invention to provide a blade-opening arrowhead wherein various types of springs and engaging elements can be used to maintain pivotally mounted blades in a normally closed position but which also provides a bias force that can be overcome by an opening force applied to the blade when in the closed position.
It is still another object of this invention to eliminate the need for consumable mechanical components, such as 0-rings, bands, wraps and the like, which are conventionally used to maintain opening blades in a closed position during flight and also during handling of the arrowhead.
It is yet another object of this invention to provide an improved design for a blade which is used in a blade-opening arrowhead.
The above and other objects of this invention are accomplished with an arrowhead that has a blade carrying body, which is also known to those skilled in the art as a ferrule. In one preferred embodiment according to this invention, at least one dull or sharpened fixed blade, preferably 2-4 dull or sharpened fixed blades, is each mounted in a fixed position with respect to the blade carrying body. In another preferred embodiment according to this invention, at least one blade, preferably 2-4 blades, are each pivotally mounted with respect to the blade carrying body. In one preferred embodiment according to this invention, a pivot shaft is mounted with respect to the blade carrying body. For example, the pivot shaft can be completely positioned within the blade carrying body so that no portion of the pivot shaft extends beyond the skin or outside surface of the blade carrying body. Each blade, fixed or pivoted, preferably hag a slot or a through hole in which the pivot shaft is matingly engaged, thus allowing the blade to be fixed or to pivot with respect to the blade carrying body.
In one preferred embodiment, each blade pivots between a normally closed position and a fully open position. In the normally closed position of the pivotal blade and in the mounted position of the fixed blade, each blade is preferably positioned such that a major or a significant portion of the blade is housed within a slot formed by the blade carrying body. In the fully closed position of the pivotal blade, a sharp edge of the blade is preferablly non-exposed for safety reasons. A major or significant portion of each blade, fixed or pivotal, is preferably housed within the blade carrying body, so that during flight the arrowhead according to this invention achieves very favorable aerodynamic qualities and characteristics.
In the fully open position of the pivotal blade, each blade preferably has a blunt edge, opposite the sharp edge, which abuts or contacts a correspondingly mateable base edge formed by the blade carrying body, preferably in an area where the blade carrying body forms the slot that houses the blade. In one preferred embodiment according to this invention, the blunt edge of the blade has an overall generally convex arcuate section and the blade carrying body has a corresponding generally concave arcuate section. Thus, when the pivotal blade is in a fully open position or when the fixed blade is in a mounted position, there is preferably but not necessarily substantial bearing surfaces contact between the blunt edge of the blade and the base edge of the blade carrying body. By providing increased surface area contact between the blade and the blade carrying body, impact forces are better transferred through the blade, through the blade carrying body and into the arrow shaft as compared to line or point contact. The arrowhead structure according to this invention acts more as an integral unit as opposed to a conventional blade-opening arrowhead wherein the impact forces are typically transferred through the pivot shaft or a similar component.
According to one preferred embodiment of this invention, the pivotal blade is held in the normally closed position by contacting an engaging element with a portion of the blade. A bias force, such as from a spring element, is used to urge the engaging element against the pivotal blade.
In one preferred embodiment according to this invention, the engaging element is a generally flattened tab which has a raised portion, which is also referred to as an upset. In another preferred embodiment according to this invention, the engaging element is a raised portion or a detent formed in a leaf spring. In such preferred embodiments, each blade has a recess and in the closed position, the raised portion, detent or upset is mateably engaged within the recess. In one preferred embodiment, the spring element can be the generally flattened tab itself, acting as a leaf spring.
In another preferred embodiment according to this invention, the locations of the raised portion and the recess can be interchanged so that the recess is formed within the generally flattened tab or leaf spring and the raised portion is formed on the blade. It is also apparent that the raised portion and the recess can have any suitably shaped cross section or overall shape.
In another preferred embodiment according to this invention, the engaging element is a plunger shaft that is slidably mounted within the blade carring body. In such preferred embodiment, the spring element is a coil spring mounted in such a manner that it normally urges the plunger shaft toward a corresponding pivotal blade. The corresponding pivotal blade has a notch which is shaped to mate with or accommodate the shape of the plunger shaft. When the blade is in the normally closed position, the plunger shaft is mated within the notch to prevent opening movement of the pivotal blade.
In the preferred embodiments of this invention as discussed above, the spring element is preferable designed so that a sufficient bias force is applied to the pivotal blade in order to prevent the pivotal blade from pivoting out of the normally closed position, even when relatively small forces are applied to the pivotal blade in an opening direction, such as when handling the arrowhead or during flight of the arrowhead. The spring element is also designed so that the bias force is easily overcome when a more significant force is applied in the opening direction, such as when the arrowhead impacts a target.
Other preferred embodiments of the engaging element and the spring element will be discussed in the following description of this invention. The blade-opening arrowhead according to this invention requires no consumable element, such as an O-ring, a band, a wrap or other similar element, in order to maintain the pivotal blades in a normally closed position. Eliminating such consumable element associated with conventional blade-opening arrowheads improves the safety aspects of the arrowhead, significantly reduces the cost for using the arrowhead by eliminating the need for a user to purchase consumable goods, and also eliminates awkward handling of the arrowhead when attempting to install such conventional consumable element particularly during a time-critical hunt.